Thermostatic control



- J. A. SPENCER THERMOSTAT I C CONTROL Filed June 1. 1922 5 '50 denly Patented Oct. 12, 1926.

UNITED STATES PATENT. orrics f on A. srENcEa, or aEvEaE, uassAcnusEr'rs, assmuoa'ro srEncEE marinara.

s'r'a'r comm, or cnusm'rs.

Application fled June 1,

The present invention relatesto thermo static control devices and more 'artlcularly Y to the general type of devices escnbed in j ample, in openin e ectrical' circuits, as their 7 .slow motion ten s tocause an are between the contacts. My earlie'r application, Serial No. 459,773, discloses a t ermostatic control device, which, b virtue of its configure- 2..tion, oifers a. relatively hi h resistance to small internal stresses cause by the tempera- 'ture. changes. At predetermined tempera tures, however, the stresses induced in the; device become sufiicient to overcome. this retending lugs f f .cesses'or o fngs' 10 ormed in the le dsupport 9. "The 0 posite mid of,

* sistance and thethermostat suddenly changes its configuration. A specific formof my m-1.; .apU-shape rthe engages with the 'vious invention contemplated the' use-of I, non-developable surface for thethermostatic element, as a means r Producing the v 2 so anceto small str and s quent tive action'of the device. I

According to the present invention, 'a quick acting thermostatic control is secured by providing-a normally flatthermostatic 85 strip or sheet, which is arched or bent between its ends. With a thermostatic. strip arched in this manner a tendency to change sha e, due to 'cha tial resisted unti a certain temperature is reac ed, when thereafter-the strip suddenly changes to a shape of-o posite curvature. In a simple form of the mvention, a thermostatic strip is retained in a bowed or arched shape by the connection of its opposite ends w1th a'rigid su port. The initial changes of temperature 0 not substantially affect the shape of such a construction but when the change of tem rature has reached a predetermined point t e bowed strip andreverses its curvature.

Still further features of the present inventionpgnsist in certain novel features of construction, combinations and'ents e ordinary thermostat comprising a may consist of a thermostatic strig) -amanner that an are "or bend is im arted thereto: To this end he strip, as in icated in temperature, is ini-- .cmamea, msacnusE'rrs, a conrona'rron. or Massa- 'raEEuosrA'rIcFconrmL. =1

. 1932. Serial no. 685,244.

ofparts hereinafter described and claimed, the advanta s of which will be obvious to those skille in the art. from the'following descri tion.

Int e accom anyin drawings illustrating the preferred orm o the invention Fig. 1

represents a plan view of a thermostatic control; F1 2is ajcross section of the control upon t e line 2+2 of Fig. 1 and illus:

trating a simple circuit connection in which the control may be embodied; Fig. 3'is' a plan view of an alternative form of control; and Fi 4; is; a cross section upon the line 0 Fig. 3 with accompanying circuit connection.

As illustrated in Figs. 1 and 2, the control indicated dissimilar at 6 and consisting of metals 0 -.thermal coefiicients of expansion intimately united. .This'stripis normally flat and is", confined between two spaced points in such in' Fig. '1 is rovided with op ositely ex- 7 which-are received in rettom of the 1 U-shape support, as. indicated. The con- Sllfl1Ct10ni$ such that the portion of the strip between the lugs .7 and the end engag i ingwiththe support!) is'maintained in an arched condition,flas illustrated in Fig.;2.

With this constructiomwhenthe tem erature of the strip is varied, no apprec able change 'in shape occurs until a certain redetermined. temperaturelimit isreac ed, when thereafter the strip suddenly changes to a shape of opposite curvature, as indicated in dot and dash lines 'in Fig. 2. This change of shape may be conveniently employed for o ni'n an electric circuit, as indicated. e circuit connections may comprises source of current designated by the terminal 15 a heating coil 16, and contacts 18, one o whichf-is'fixed and one of which is mounted'upon the free end of the strip; It will be evident that the. heating coil may beembodied inla-suitable type {if electrical apparatus, as a sadiron, an

tion to automatically opening the circuit upon reaching a predetermined temperature limit, this form of thermostatic control automatically returns to normal position when the temperature has dropped to a predetermined point, the thermostatic strip at this time reversing its curvature and returning to the position shown in full lines.

In addition to the construction shown in Figs. 1 and 2, the construction shown in Figs. 3 and 4 may also be usefully emplo ed for securing the sudden opening of an e ectric circuit. In this construction, as indicated in the drawings, the thermostatic strip 6 may be in the form of a hollow rectangle having a resilient metallic member 12 rigidly connected to opposite endsby rivets 13. This metallic. strip which may be of spring steel has the opposite end por-s tions deflected slightly, as shown in Fig. 4, for a purpose to be presently described. lVith such a'construction initial changes in temperature do not materially change the position of the strip 12. Upon reachin a predetermined temperature limit, the istortion of the ends of the rectangle 6 snaps the member 12 therethrough into the position shown in dotted lines, causing an abrupt opening of the circuit. As indicated in the drawings, the circuit may comprise terminals 15, heating coil 16, together with the stationary and movable contacts .18, one of which is carried upon the member 12.

. While it is preferred to employ the spe- 'cific construction and arrangement of parts shown and described it will be understood that this construction and arrangement is not essential except so far as specified in the claims and may be changed or modified without departing from the broader features of the invention.

The invention having been described, what is claimed is 1.'A thermostatic control comprising a normally fiatthermostatic strip, a support, and connections between the strip and support for maintaining an arched condition of the strip between two separated points, the strip suddenly changing shape upon reaching a predetermined temperature.

.2. A thermostatic control'comprisin g elongated thermostatic strip, a rigid support, and connections between the stri and support, for maintaining the strip in an arched condition between points s aced from one another, the strip suddenly c ang-' mg shape upon reaching a predetermined temperature.

3'. A thermostat comprising a bimetallic sheet of thermostaticmetal, means forcing the sheet to remain normally concave or dished on the side having the higher thermal coefiicient of expansion and preventing free expansion of said sheet when heats said sheet when heated tending to pass abruptly and automatically to a position of an opposite curvature, and passing abruptly and automatically to said position at a predetermined temperature.

4. A thermostat comprising a bimetallic sheet of thermostatic metal, means forcing the sheet to remain normally concave or dished on the side having the higher thermal coeflicient of expansion and preventin free epxansion of said sheet when heate said sheet when heated passing abruptly and automatically to a position of an opposite curvature, and resuming its original position abruptly and automatically when cooled to a predetermined temperature.

5. A thermostat comprising composite thermostatic material and means, other than the material itself, for confining a portion of said material against free change of shape, thereby settln up internal stresses the magnitude of w llCh changes upon changes of temperature, the thermostat reaching a condition of instability at a predetermined temperature during heating and at a predetermined temperature during cooling, the devicethen abruptly changing I its shape.

7 6; A thermostat comprising composite thermostatic material and means, other than the material itself, for confining at least a portion of said material against free change of shape, thereby setting u internal stresses themagnitude of Whicli changes upon changes of temperature, the

thermostat reaching a condition of instability at a predetermined temperature during heating and at predetermined temperature during cooling, the material then abruptly changing its shape due -.to release of internal stresses stored u in the material by reason of the change 0 temperature to said predetermined value.

7. A thermostat comprising composite thermostatic material and means, other than thematerial itself, for confining at least a portion of said material against free expansion thereby setting up internal stresses t e ma itude of which changes upon changes-o temperature, the thermostat. reaching a condition of instability when it is heated to a predetermined tem= perature, the material then abruptly changmg its shape due to release of internal strtlasses theretofore stored up in the materia 4 8, A thermostat comprising composite thermostatic material and means, other than the material itself,

.when itiscooled to a predetermined telnfor confining at least a portion of said material against free I temperature, the thermo .9. A thermostat comprising thermostatic composite material confined against free change of shape by means external to the material itsel, "w ereby internal stresses are set up; the magnitude of which changes upon changes of temperature, the material being so confined that change of its shape is a discontinuous function of the temperature.

10. A thermostat comprisin a sheet of composite thermostatic material, external non-composite means for confining at least a portionof said sheet against free change of shape, thereby setting up internal stresses the magnitude of which changes upon changes of 'tem erature, the thermostat,

being so shaped t at change of its shape is a a discontinuous function otthe temperature.

mostatic sheet 11. A thermostat having a composite therortion curved and separate means stressed by the expansion of said portion when heated, and opposing the expan- 'sion of said portion, 'said portion when sion of said portion, sa1

heated to a predetermined temperature tending to ass abruptly and automatically to anothers ape.

12. A thermostat-having a composite thermostatic sheet portion curved and means stressed by the expansion of said portion when heated and which op oses the expanportion when heated to a predetermined temperature tending to pass abruptly and automatically to another shape and tending to resume its original sha --automatically and abruptly when coole to a predetermined temperature.

'13. A thermostat having a composite thermostatic sheet portion and means stressed by the expansion or contraction of said portion with change-of temperature and o posing said expansion or contraction, said portion when it attains a predetermined temperature tending to pass abruptly and automatically to another shape.

14:. A thermostat comprising a plurality of united components having difi'erent coefiicients of expansion, means normally flexing said components in one direction, tending to flatten in response to temperature change in one sense, thereby setting u stresseswhich oppose said tendency, unt1 a predetermined temperature is reached, the stresses then changing the flexure.

15. A thermostatic device comprising portions arranged to react upon each other with change of temperature to 'set up stresses the magnitude of which changes upon change of temperature, one of the portions being formed of components having difl'erentcoeflicients of expansion, the device reaching a conditionof instability at a predetermine temperature by virtue of the arrangement of said portions and as a result of the change of temperature, whereupon said stresses become effective to change abruptly the relative position 0t said portions.

JOHN A. SPENCER. 

